The manufacturing technology of integrated circuits (IC) is a complex process; and it may be updated for approximately every 18 months to 24 months. A major parameter for evaluating the manufacturing technology of ICs is the minimum feature size of the ICs. The minimum feature size of ICs is also referred as a critical dimension (CD). The critical dimension of ICs has been reduced from the initial size of 125 μm to the current size of 0.13 μm or below. Such a reduction of the critical dimension of ICs may cause forming millions of devices in a single chip to be possible.
Photolithography has always been a major driving force of the development of the manufacturing process of ICs. Comparing with other individual fabrication processes of the manufacturing of ICs, a photolithography process may be a revolutionary contribution to the improvement of ICs. Before performing a photolithography process, the structure of ICs may be replicated (or written) on a mask larger than the wafer of ICs by certain processes. The mask may be made of quartz or glass, etc. Then, the structure of ICs on the mask may be transferred onto the wafer using an ultraviolet light with a certain wavelength generated by a photolithography apparatus. For example, the wavelength of the ultraviolet light may be 248 nm.
When the circuit structure on the mask is transferred to the wafer by a photolithography process, a pattern distortion may occur, especially when the technical node enters into 0.13 μm or below. If such a distortion is not corrected, the entire manufacturing technology (process) may fail. The pattern distortion may be caused by the optical proximity effect (OPE). The exposure system of the photolithography apparatus forms an image using a partial coherent light system. Theoretically, the amplitude of the spectrum of the image may distribute differently along different directions. However, because of the limitation of the imaging system caused by the optical diffraction and the non-linear filtering when the critical dimension becomes significantly small, the energy of the exposure light may be lost in certain directions during the photolithography process. Such an energy lost may cause the image space to have a rounding and shrinking effect, etc.; and such an effect may be referred as the optical proximity effect (OPE).
In order to correct the pattern distortion caused by the OPE, a widely used method in the field of semiconductor manufacturing is to do a pre-structure-correction on the mask. Such a correction method is referred as an optical proximity correction (OPC). The basic principle of the OPC is to pre-correct the patterns of the IC design so as to cause the pre-correction of the patterns to be able to compensate the OPE caused by the photolithography apparatus. Therefore, by using the mask having the patterns formed by the OPC, after the photolithography process, the initially desired patterns of the ICs may be obtained.
The test patterns of the existing OPC models are usually stored in an OPC model database; and can be called when they are needed. However, the quantity of the stored OPC models (the mask patterns obtained be the OPC process) in the OPC model database may be limited; and it may be unable to include all the new circuit patterns (layout) designed by customers. The disclosed methods and systems are directed to solve one or more problems set forth above and other problems.